A device for a hull of a remotely operated vehicle is described, in which several frame elements provided by a curable material form a frame, the frame elements containing a carcass formed of a buoyant material. A method of forming the hull is described as well.
When building a remotely operated vehicle (ROV) which is to operate at great water depths, of several thousand meters, that is to say, it is of vital importance that the structure is strong enough to withstand the high water pressure to which the vehicle may be exposed. At the same time, the vehicle must exhibit sufficient buoyancy, and the framework (hull) must be able to accommodate the equipment with which the vehicle is to be fitted out.
It is known to provide the necessary buoyancy in the form of one or more blocks formed of a suitable buoyant material on the vehicle frame, for example on the top of the frame. It is also known to use gas-filled compartments in the frame, for example by the frame being formed, at least partially, of closed pipes. The drawback of gas-filled compartments is that it is difficult for them to withstand the extremely high pressure to which the ROV is exposed at the water depths that are relevant today. Attempts have therefore been made to fill frame pipes with buoyancy means which can exhibit sufficient compressive strength. It is known to fill frame pipes with a liquid material which, after setting, exhibits a suitable specific weight and sufficient compressive strength. Examples of such materials are lightweight concrete and expanding plastics. It turns out that under the prevailing conditions, such materials do not have the properties required. Among other things, the closed volumes will result in expansion, curing et cetera not developing in the same way as when the materials can be vented and moisture, solvents et cetera may be carried away.